The present invention is directed generally to a fiber optic device, and more particularly to an fiber optic isolator having multiple ports.
Optical fibers find many uses for directing beams of light between two points. Optical fibers have been developed to have low loss, low dispersion, polarization maintaining properties and can also act as amplifiers. As a result, optical fiber systems find widespread use, for example in optical communication applications.
However, one of the important advantages of fiber optic beam transport, that of enclosing the optical beam to guide it between terminal points, is also a limitation. There are several optical components, important for use in fiber systems or in fiber system development, that are not implemented in a fiber-based form where the optical beam is guided in a waveguide. Instead, these optical components are implemented in a bulk form that light must freely propagate through. An example of such a component is an optical isolator. Consequently, the inclusion of a bulk optical isolator in an optical fiber system necessitates that the optical fiber system have a section where the beam path propagates freely in space, rather than being guided within a fiber.
Free space propagation typically requires that the beam from each fiber be collimated and directed along the axis of the bulk component being used in the free-space propagation section. Usually, this necessitates that a collimating lens be positioned at the input fiber to collimate the incoming light and a focusing lens be positioned at the output fiber to focus the freely propagating light into the output fiber. The free-space propagation section lies between the two lenses. The introduction of a free-space propagation section requires that the collimating lens and the focusing lens are each aligned to their respective fibers and also that the focusing lens is correctly aligned relative to the collimated beam path from the collimating lens. The alignment of the corresponding collimating and focusing lens pairs remains critical, irrespective of the number of fibers. Accordingly, the alignment process becomes more complex and time consuming when multiple fibers require the alignment of multiple collimating and focusing lenses into multiple isolators.
In addition, each collimating and focusing lens and each fiber has to be supported transversely. The provision of transverse support increases the total cross-section required by each fiber/lens assembly, thus resulting in a large system.
Accordingly, there is a need for an improved approach to introducing a free-space propagation section into fiber optic systems that is simpler to align and is more compact. Additionally, there is a need for compact isolators that are capable of handling several inputs.